The present invention is directed to ink-jet printers and, more particularly, to ink-jet printers employing an off-axis ink delivery system for replenishing on-axis print cartridges with ink.
In a conventional ink jet printer, ink is deposited on record media such as paper via a disposable pen, the pen being mounted on a carriage for reciprocation across the paper""s face. Ink is ejected through the pen""s printhead, the printhead being connected to a volume of ink which is stored in a reservoir onboard the pen. When the ink reservoir is depleted, the pen is removed from the carriage, discarded, and replaced with a new pen. An example of such a pen is disclosed in U.S. Pat. No. 4,771,295, which is entitled xe2x80x9cThermal Ink Jet Pen Body Construction Having Improved Ink Storage and Feed Capabilityxe2x80x9d, and which is commonly owned herewith. The disclosure of that patent is incorporated herein by this reference.
In order to extend the useful life of ink jet pens, several off-axis ink supply approaches have been suggested whereby the pen""s onboard ink reservoir is refilled. These approaches have included the use of a second, off-board ink supply, generally in the form of a larger ink reservoir positioned at a location which is remote from the pen. As the pen""s onboard supply of ink is depleted, substitute ink is delivered from the off-board reservoir through an arrangement of one or more tubes. The larger ink reservoir thus allows for use of the pen beyond the duration of the its onboard ink supply, effectively extending the pen""s lifetime to coincide with the lifetime of the its associated printhead. An illustrative example of such an approach is provided in U.S. Pat. No. 4,831,389, which is entitled xe2x80x9cOff Board Ink Supply System and Process for Operating an Ink Jet Printerxe2x80x9d, and which is commonly owned herewith. The disclosure of that patent is incorporated herein by this reference.
Although known off-axis ink supply approaches generally have been effective in extending the lifetime of a printer""s pen, there remains room for improvement, particularly in the manner by which ink is delivered to the pen. In the past, ink has been delivered via flexible tubing which runs from the off-board ink supply to the reservoir within the pen. The tubing generally extends as a linear segment, each tube having a length which allows for reciprocation of the pen. As the pen reciprocates, and the distance between the pen and off-board reservoir changes, the tubing is bent over on itself so as to take up the resulting slack.
This tubing arrangement has led to a number of problems, due in large part, to the effects of tube bending during reciprocation of the pen. Such bending, for example, will often produce an unacceptably high stress on the tube, increasing tube fatigue, and correspondingly decreasing the lifetime of the tube. In addition, bending of the tubes may result in an undesirably high torque on the pen carriage, increasing the power required to drive the pen. Further, because the bending of tubes requires a significant amount of clearance, the use of off-axis ink supplies has resulted in a significant increase in the printer""s size. The latter problem is particularly troublesome where a multi-color pen is employed, it being necessary to run a plurality of tubes (one for each color) between the reservoir and the reciprocating pen.
In spite of the foregoing, other solutions, such as the use of a rigid tube, as disclosed, for example, in commonly-owned U.S. Pat. No. 5,691,754, entitled xe2x80x9cRigid Tube Off-Axis Ink Supplyxe2x80x9d, do not offer the potential advantages provided by flexible tubing, or conduit. Specifically, flexible conduit permits more facile movement of the print heads.
In addition to the foregoing, the conduit must also contain and deliver ink under various environmental conditions and usages. The conduit must balance the following requirements:
the conduit must be sized large enough to deliver the required amount of ink flow;
stiffness must not affect carriage dynamics, or pen seating;
bend diameters must be kept to a minimum for product size/layout;
the conduit must withstand five years of carriage cycles;
the conduit must maintain properties over shipping and operating temperatures;
the conduit must be able to withstand chemical attack from inks or other outside contaminants;
the conduit must be able to contain ink without letting air diffuse in or water vapor diffuse out;
the conduit must be able to bend in small arcs for routing in the product without kinking; and
the conduit must be consistently processable and cost effective.
Defining a material is challenging because several of these requirements pull material properties in opposite directions. Work on tubing solutions has been on-going for the past several years and has resulted in a number of solutions, but none have been totally satisfactory to date. The technologies and materials that have been available are limited and the products have had to make large sacrifices. One printer product was released with a Teflon-based material (polychlorotrifluoroethylene; PCTFE), which had fatigue issues, and then was changed to another Teflon-type material (fluorinated ethylene propylene; FEP), which had processing and diffusion issues. Another printer product started with Saran, which is polyvinylidene dichloride, which had processing and fatigue issues, and then was changed to low density polyethylene, which was a compromise to diffusion. The available options for materials that adequately satisfy the above-listed design requirements have, for the most part, been exhausted.
Thus, there remains a need for a fluid transport conduit that allows design freedom while using the existing material base and is impermeable to air and ink while retaining bending flexibility.
In accordance with the present invention, a fluid transport conduit for conveying ink-jet ink from a reservoir to a printhead is provided. The fluid transport conduit comprises an inner layer that is flexible and comprises a barrier to liquid and an outer layer that is a barrier to air and is more compliant than the inner layer, with the inner layer bonded to the outer layer.
Depending on the materials used for the inner layer and the outer layer, an adhesive may be used to bond the two layers together. Alternatively, the inner and outer layers may be bonded together naturally by a co-extrusion process. Further, either or both of the inner layer and outer layer may include more than one material for further tailoring the properties of the conduit.
Employing an inner layer that is flexible and is a barrier to liquid and an outer layer that is more compliant than the inner layer and is a barrier to air results in a fluid transport conduit that is flexible during movement of the printhead, yet protects the ink from the effects of air, while preventing leakage of ink into the printer.